• Beyond masking: Endangered Stephen's kangaroo rats respond to traffic noise with footdrumming

      Shier, Debra M.; Lea, Amanda J.; Owen, Megan A. (2012)
      ... Roads and road margins on and off reserves serve as dispersal corridors and refugia for SKR and other semifossorial taxa; these areas may therefore function as ecological traps if anthropogenic roadway noise negatively affects population persistence.
    • Giant pandas attend to androgen-related variation in male bleats

      Charlton, Benjamin D.; Swaisgood, Ronald R.; Zhihe, Zhang; Snyder, Rebecca J. (2012)
      Although androgen-dependant traits are predicted to signal overall male quality, no study has examined the response of a nonhuman animal to variation in a known acoustic cue to male androgen levels (steroid hormones that are key drivers of male sexual behaviour). Here, we use a single-speaker approach to present male and female giant pandas with re-synthesised male bleats representing callers with high and low androgen levels. Our results revealed that male and female giant pandas had significantly greater-looking responses, spent more time pacing, and were faster to respond to playbacks of bleats simulating high androgen males. When we analysed the sexes separately, a slightly different response pattern was revealed: whereas males and females still had significantly greater-looking responses and were faster to respond to bleats simulating high androgen males, only male giant pandas tended to spend more time pacing. These findings suggest that vocal cues to male androgen levels are functionally relevant to male and female giant pandas during the breeding season, and constitute the first demonstration that a nonhuman animal could be using a vocal signal to assess male hormonal state. We go on to discuss the ecological relevance of signalling androgen levels in this species’ sexual communication and the possible application of our results to conservation breeding.
    • The role of bioacoustic signals in koala sexual selection: Insights from seasonal patterns of associations revealed with GPS-proximity units

      Ellis, William A.; FitzGibbon, Sean; Pye, Geoffrey W.; Whipple, Bill; Barth, Ben; Johnston, Stephen; Seddon, Jenny; Melzer, Alistair; Higgins, Damien; Bercovitch, Fred B. (2015)
      Despite being a charismatic and well-known species, the social system of the koala (Phascolarctos cinereus—the only extant member of the family Phascolarctidae) is poorly known and much of the koala’s sociality and mating behaviors remain un-quantified. We evaluated these using proximity logging-GPS enabled tracking collars on wild koalas and discuss their implications for the mating system of this species. The frequency and duration of male-female encounters increased during the breeding season, with male-male encounters quite uncommon, suggesting little direct mating competition. By comparison, female-female interactions were very common across both seasons. Body mass of males was not correlated with their interactions with females during the breeding season, although male size is associated with a variety of acoustic parameters indicating individuality. We hypothesise that vocal advertising reduces the likelihood of male-male encounters in the breeding season while increasing the rate of male-female encounters. We suggest that male mating-season bellows function to reduce physical confrontations with other males allowing them to space themselves apart, while, at the same time, attracting females. We conclude that indirect male-male competition, female mate choice, and possibly female competition, mediate sexual selection in koalas.